[Code scan] Resolve example input files relative to each script directory

[njzjz]

This issue is a result of a Codex global code scan of deepmodeling/fpop at commit b05b337590c31a5237b2dcbd9c0833b841c08cd4.

Relevant code:

fpop/examples/vasp/preprunvasp.py

Lines 67 to 83 in b05b337

	confs = ["POSCAR-1","POSCAR-2","POSCAR-3"]
	vasp_inputs = VaspInputs(0.4,'test_incar',{'Na':'test_potcar'},True) # kspacing incar potcar kgamma
	prep_run_step = Step(
	'prep-run-step',
	template = steps,
	parameters = {
	'type_map' : ["Na"],
	'prep_image_config' : prep_image_config,
	'run_image_config' : run_image_config,
	'inputs' : vasp_inputs,
	'optional_input' : {"conf_format":"vasp/poscar"},
	'backward_list' : ["OUTCAR","CONTCAR"],
	},
	artifacts = {
	"confs" : upload_artifact(confs),
	},

fpop/examples/cp2k/prepruncp2k.py

Lines 67 to 85 in b05b337

	confs = ["POSCAR-1","POSCAR-2","POSCAR-3"]
	cp2k_inputs = Cp2kInputs('input.inp') # input files
	prep_run_step = Step(
	'prep-run-step',
	template = steps,
	parameters = {
	'type_map' : ["Na"],
	'prep_image_config' : prep_image_config,
	'run_image_config' : run_image_config,
	"log_name" : "output.log",
	'inputs' : cp2k_inputs,
	'optional_input' : {"conf_format":"vasp/poscar"},
	'backward_list' : ["output.log"],
	},
	artifacts = {
	"confs" : upload_artifact(confs),
	},

fpop/examples/abacus/preprunvasp.py

Lines 67 to 83 in b05b337

	confs = ["POSCAR-1","POSCAR-2","POSCAR-3"]
	abacus_inputs = AbacusInputs('INPUT',{'Na':'Na_ONCV_PBE-1.0.upf'})
	prep_run_step = Step(
	'prep-run-step',
	template = steps,
	parameters = {
	'type_map' : ["Na"],
	'prep_image_config' : prep_image_config,
	'run_image_config' : run_image_config,
	'inputs' :abacus_inputs,
	'optional_input' : {"conf_format":"vasp/poscar"},
	'backward_list' : ["OUT.ABACUS","log"],
	},
	artifacts = {
	"confs" : upload_artifact(confs),
	},

Problem:
The example scripts refer to bundled input files with current-working-directory-relative paths such as POSCAR-1, test_incar, test_potcar, input.inp, INPUT, and Na_ONCV_PBE-1.0.upf.

Running an example from the repository root with a normal command such as:

python examples/vasp/preprunvasp.py

makes the script look for test_incar and POSCAR-1 in the repository root, even though those files live under examples/vasp/. The same pattern exists in the CP2K and ABACUS examples.

Expected behavior:
Each example should resolve local inputs from Path(__file__).resolve().parent, so the examples work regardless of the caller's current working directory.